1. Field of the Invention
The invention relates to a method of storing and recycling photographic processing solutions, and in particular, to a method for recycling process overflow solutions in a preserved condition.
2. Description of the Related Art
During the processing of silver halide photographic elements, the "working" baths typically require replenishment to replace exhausted, evaporated and/or photographic element entrained components.
The degradation of processing solutions occurs as a result of repeated participation in photographic development, fixing, and/or bleaching; and inadvertent oxidation phenomenon. Additionally, the activity of the processing baths such as the developer bath can be inhibited due to contamination attributable to the accumulation of compounds, predominantly halides, which have been inadvertently leached from the photographic film element.
When a replenisher is introduced into a working bath, a corresponding mass-volume in the working bath will typically be displaced as overflow. As a result, steps must be taken to handle the displaced solution. Moreover, the amount of overflow can be considerable, particularly in a large photographic processing facility.
In the past, and in order to simplify the problem of treating and handling the developer overflow, exhausted developer overflow was typically discharged to a drain or collected for waste disposal. For example, see U.S. Pat. No. 5,063,141.
However, ever-increasingly stringent environmental regulations have compelled far more conscientious approaches in the handling of developer overflow. As a result, developer recycling is now practiced to a greater extent than in former years. In this regard, developer recycling involves treatment of the recycled material prior to reuse. This treatment can involve either regeneration, i.e., the addition of fresh chemicals to the solution, or purification, i.e., removal of deleterious byproducts, e.g., halides, from the solution.
Unfortunately, there are certain limitations to the present practices that make recycling unattractive. For example, there is the difficulty to optimize recycle rates for process solutions that achieve no waste discharge and at the same time avoid the buildup of critical levels of oxidation products and extractives from photographic material that degrade processing. The situation is especially critical where there is low volume turnover (or lower utilization) in small scale photographic processing facilities.
Another approach to the problem of handling overflow has been to severely reduce or prevent developer overflow altogether, and, thus, preclude the need to handle developer overflow. In this regard, attempts have been made to reduce the amount of developer overflow created by careful manipulation of the process protocol, e.g., adjusting the developer bath temperature, in order to possibly accomplish processing at a reduced developer replenishment rate. For example, see U.S. Pat. No. 5,068,170.
Other related proposals have been made to eliminate developer overflow altogether by careful monitoring and maintaining of specific developer/replenisher compositions in the primary tank and as used in conjunction with a prescribed photographic composition. For example, see U.S. Pat. Nos. 4,997,749 and 5,004,676.
Of course, these approaches for reducing overflow only allow for developer replenishment equal to the relatively small amounts of developer bath lost to evaporation or entrainment on the photographic material. Moreover, these past approaches for reducing (if not eliminating) developer overflow are not without their drawbacks. Namely, these past approaches are largely unsatisfactory because they impose severe constraints on development bath protocol and compositions, and even on the type of photographic film and paper that can be processed in the development bath. These sacrifices in the versatility of the development bath are not acceptable in many circumstances.
In view of the foregoing, some recognition has emerged in the art regarding the design of improved systems for recycling used developer solution. For example, see U.S. Pat. Nos. 5,057,858 and 4,983,504.
Moreover, the reuse of other processing liquids has also been recently addressed. For instance, a bleach-fix regeneration kit that was recently disclosed in U.S. Pat. No. 5,055,382 addresses the need to reuse bleach-fix solutions.
The difficulties associated with handling of overflow solutions are particularly apparent in the area of "one hour" development, i.e., mini-labs. In fact, chemicals used in the one hour film development processing market are typically added to the process "as necessary", or even automatically, and the overflow chemical is usually discarded as unusable.
In fact, at most mini-labs, multiple solutions are typically introduced into a single overflow container. Thus, most mini-labs are not currently constructed to collect and reuse the overflow because such an undertaking would require a separate collection tank for each chemical to be reused.
Recent advances in chemical technologies have made it easier for mini-labs to consider recycling the overflow solutions. However, despite these efforts the art has been largely unable to provide a facile, cost-effective method to recycle most, if not all of one or more photographic processing solutions, and particularly developer overflow solution caused by replenishment.